Q16. 
$12$ chairs are arranged in a row and are numbered $1$ to $12$. $4$ men have to be seated in these chairs so that the chairs numbered $1$ ans$8$ should be occupied and no two men occupy adjacent chairs. Find the number of ways the task can be done. 
A.  $360$ 

B.  $384$ 

C.  $432$ 

D.  $470$ 
Q17. 
How many words can be formed by rearranging the letters of the word $ASCENT$ such that $A$ and $T$ occupy the first and last position respectively? 
A.  $5!$ 

B.  $4!$ 

C.  $6! – 2!$ 

D.  $6!/2!$ 
Q18. 
If ${^6P_r} = 360$ and ${^6C_r} = 15$ find $r$? 
A.  $3$ 

B.  $4$ 

C.  $5$ 

D.  $6$ 
Q19. 
In how many ways can six different rings be worn on four fingers of one hand? 
A.  10 

B.  12 

C.  15 

D.  16 
Q20. 
There are $12$ yes or no questions. How many ways can these be answered? 
A.  $4096$ 

B.  $2048$ 

C.  $1024$ 

D.  $144$ 